erl_call

COMMAND

erl_call

COMMAND SUMMARY

Call/Start a Distributed Erlang Node

DESCRIPTION

erl_call makes it possible to start and/or communicate with
a distributed Erlang node. It is built upon the erl_interface
library as an example application. Its purpose is to use an Unix shell script to interact with a distributed Erlang node. It performs all
communication with the Erlang rex server, using the standard Erlang RPC facility. It does not require any special
software to be run at the Erlang target node.

The main use is to either start a distributed Erlang node
or to make an ordinary function call. However, it is also
possible to pipe an Erlang module to erl_call and have it
compiled, or to pipe a sequence of Erlang expressions to be evaluated
(similar to the Erlang shell).

Options, which cause stdin to be read, can be used with
advantage
as scripts from within (Unix) shell scripts. Another
nice use of erl_call could be from (http) CGI-bin scripts.

EXPORTS

(optional): Applies the specified function
and returns the result. Mod must be specified, however
[] is assumed for unspecified Fun and Args. Args should
be in the same format as for erlang:apply/3. Note
that this flag takes exactly one argument, so quoting
may be necessary in order to group Mod, Fun
and Args, in a manner dependent on the behavior
of your command shell.

-c Cookie

(optional): Use this option to specify a certain cookie. If no cookie is specified, the ~/.erlang.cookie file is read and its content are used as cookie. The Erlang node we want to communicate with must have the same cookie.

-d

(optional): Debug mode. This causes all IO to be output
to the file ~/.erl_call.out.Nodename, where Nodename
is the node name of the Erlang node in question.

-e

(optional): Reads a sequence of Erlang expressions, separated
by ',' and ended with a '.', from stdin until
EOF (Control-D). Evaluates the expressions and returns the result from
the last expression. Returns {ok,Result} if successful.

-h HiddenName

(optional): Specifies the name of the hidden node
that erl_call represents.

-m

(optional): Reads an Erlang module from stdin and
compiles it.

-n Node

(one of -n, -name, -sname is required):
Has the same meaning as -name and can still be used for
backwards compatibility reasons.

-name Node

(one of -n, -name, -sname is required): Node is the name of the node to be
started or communicated with. It is assumed that
Node is started with erl -name, which means that fully
qualified long node names are used.
If the -s option is given, an Erlang node will (if necessary)
be started with erl -name.

-q

(optional): Halts the Erlang node specified
with the -n switch. This switch overrides the -s switch.

-r

(optional): Generates a random name of the hidden node
that erl_call represents.

-s

(optional): Starts a distributed Erlang node if necessary.
This means that in a sequence of calls, where the '-s'
and '-n Node' are constant, only the first call will start
the Erlang node. This makes the rest of the communication
very fast. This flag is currently only available on the Unix platform.

-sname Node

(one of -n, -name, -sname is required): Node is the name of the node to
be started or communicated with. It is assumed that Node is started with erl -sname which means that short node names are used.
If -s option is given, an Erlang node will be started (if necessary) with erl -sname.

-v

(optional): Prints a lot of verbose information.
This is only useful for the developer and maintainer of erl_call.

-x ErlScript

(optional): Specifies another name of the Erlang start-up script
to be used. If not specified, the standard erl start-up script
is used.

Examples

Starts an Erlang node and calls erlang:time/0.

erl_call -s -a 'erlang time' -n madonna
{18,27,34}

Terminates an Erlang node by calling erlang:halt/0.

erl_call -s -a 'erlang halt' -n madonna

An apply with several arguments.

erl_call -s -a 'lists map [{math,sqrt},[1,4,9,16,25]]' -n madonna

Evaluates a couple of expressions. The input ends with EOF (Control-D).